UPDATE 2-Buffett's Berkshire has first loss since 2001

* ConocoPhillips, derivatives hurt results

* Economy weighs on several businesses

* Insurance units post better results (Adds financial details, background on derivatives)

By Jonathan Stempel

NEW YORK, May 8 (Reuters) - Warren Buffett's Berkshire Hathaway Inc (BRKa.N)(BRKb.N) posted its first quarterly loss since 2001, hurt by losses on derivative contracts and a big investment in the oil company ConocoPhillips (COP.N).

The net loss for the Omaha, Nebraska-based insurance and investment company was $1.53 billion, or $990 per Class A share, and compared with a profit of $940 million, or $607, a year earlier.

Excluding investments, operating profit fell 12 percent to $1.71 billion, or $1,100 per share, from $1.93 billion, or $1,247. That profit was in line with the $1.7 billion that Buffett estimated at Berkshire's annual meeting last Saturday.

Analysts on average expected operating profit of $1,087 per share, according to Reuters Estimates. Revenue fell 9.5 percent to $22.78 billion.

Buffett said many of Berkshire's nearly 80 businesses were hurt by the economic recession and lower consumer spending. The company last had a quarterly loss in the third quarter of 2001, resulting from insurance claims tied to the Sept. 11 attacks.